The Obesity Code. Jason Fung

overweight category (body mass index of 25 to 29.9), but bordering on obese (body mass index greater than 30). They were followed for 7.5 years to see if the doctor-recommended diet reduced obesity, heart disease and cancer as much as expected.

      The group that received dietary counseling succeeded. Daily calories dropped from 1788 to 1446 a day—a reduction of 342 calories per day for over seven years. Fat as a percentage of calories decreased from 38.8 percent to 29.8 percent, and carbohydrates increased from 44.5 percent to 52.7 percent. The women increased their daily physical activity by 14 percent. The control group continued to eat the same higher-calorie and higher-fat diet to which they were accustomed.

      The results were telling. The “Eat Less, Move More” group started out terrifically, averaging more than 4 pounds (1.8 kilograms) of weight loss over the first year. By the second year, the weight started to be regained, and by the end of the study, there was no significant difference between the two groups.

      Did these women perhaps replace some of their fat with muscle? Unfortunately, the average waist circumference increased approximately 0.39 inches (0.6 centimeters), and the average waist-to-hip ratio increased from 0.82 to 0.83 inches (2.1 centimeters), which indicates these women were actually fatter than before. Weight loss over 7.5 years of the Eat Less, Move More strategy was not even one single kilogram (2.2 pounds).

      This study was only the latest in an unbroken string of failed experiments. Caloric reduction as the primary means of weight loss has disappointed repeatedly. Reviews of the literature by the U.S. Department of Agriculture¹³ highlight this failure. All these studies, of course, serve only to confirm what we already knew. Caloric reduction doesn’t cause lasting weight loss. Anybody who has ever tried it can tell you.

      Many people tell me, “I don’t understand. I eat less. I exercise more. But I can’t seem to lose any weight.” I understand perfectly—because this advice has been proven to fail. Do caloric-reduction diets work? No. The Women’s Health Initiative Dietary Modification Trial was the biggest, baddest, most kick-ass study of the Eat Less, Move More strategy that has ever been or ever will be done—and it was a resounding repudiation of that strategy.

      What is happening when we try to reduce calories and fail to lose weight? Part of the problem is the reduced metabolism that accompanies weight loss. But that’s only the beginning.

       HUNGER GAMES

      THE CALORIES IN, Calories Out plan for weight loss assumes that we have conscious control over what we eat. But this belief ignores the extremely powerful effect of the body’s hormonal state. The defining characteristic of the human body is homeostasis, or adaptation to change. Our body deals with an ever-changing environment. In response, the body makes adjustments to minimize the effects of such changes and return to its original condition. And so it is, when the body starts to lose weight.

      There are two major adaptations to caloric reduction. The first change, as we have seen, is a dramatic reduction in total energy expenditure. The second key change is that the hormonal signals that stimulate hunger increase. The body is pleading with us to eat in order for it to regain the lost weight.

      This effect was demonstrated in 2011, in an elegant study of hormonal adaptation to weight loss.¹⁴ Subjects were given a diet of 500 calories per day, which produced an average weight loss of 29.7 pounds (13.5 kilograms). Next, they were prescribed a low-glycemic-index, low-fat diet for weight maintenance and were encouraged to exercise thirty minutes per day. Despite their best intentions, almost half of the weight was regained.

      Various hormonal levels, including ghrelin—a hormone that, essentially, makes us hungry—were analyzed. Weight loss significantly increased ghrelin levels in the study’s subjects, even after more than one year, compared to the subjects’ usual baseline.

      What does that mean? It means that the subjects felt hungrier and continued to feel so, right up to end of the study.

      The study also measured several satiety hormones, including peptide YY, amylin and cholecystokinin, all of which are released in response to proteins and fats in our diet and serve to make us feel full. This response, in turn, produces the desired effect of keeping us from overeating. More than a year after initial weight loss, the levels of all three satiety hormones were significantly lower than before.

      What does that mean? It means that the subjects felt less full.

      With increased hunger and decreased satiety, the desire to eat rises. Moreover, these hormonal changes occur almost immediately and persist almost indefinitely. People on a diet tend to feel hungrier, and that effect isn’t some kind of psychological voodoo, nor is it a loss of willpower. Increased hunger is a normal and expected hormonal response to weight loss.

      Dr. Keys’s Minnesota Starvation Experiment first documented the effect of “semi-starvation neurosis.” People who lose weight dream about food. They obsess about food. All they can think about is food. Interest in all else diminishes. This behavior is not some strange affliction of the obese. In fact, it’s entirely hormonally driven and normal. The body, through hunger and satiety signaling, is compelling us to get more food.

      Losing weight triggers two important responses. First, total energy expenditure is immediately and indefinitely reduced in order to conserve the available energy. Second, hormonal hunger signaling is immediately and indefinitely amplified in an effort to acquire more food. Weight loss results in increased hunger and decreased metabolism. This evolutionary survival strategy has a single purpose: to make us regain the lost weight.

      Functional magnetic resonance imaging studies show that areas of the brain controlling emotion and cognition light up in response to food stimuli. Areas of the prefrontal cortex involved with restraint show decreased activity. In other words, it is harder for people who have lost weight to resist food.¹⁵

      This has nothing whatsoever to do with a lack of willpower or any kind of moral failure. It’s a normal hormonal fact of life. We feel hungry, cold, tired and depressed. These are all real, measurable physical effects of calorie restriction. Reduced metabolism and the increased hunger are not the cause of obesity—they are the result. Losing weight causes the reduced metabolism and increased hunger, not the other way around. We do not simply make a personal choice to eat more. One of the great pillars of the caloric-reduction theory of obesity—that we eat too much because we choose to—is simply not true. We do not eat too much because we choose to, or because food is too delicious, or because of salt, sugar and fat. We eat too much because our own brain compels us to.

       THE VICIOUS CYCLE OF UNDER-EATING

      AND SO WE have the vicious cycle of under-eating. We start by eating less and lose some weight. As a result, our metabolism slows and hunger increases. We start to regain weight. We double our efforts by eating even less. A bit more weight comes off, but again, total energy expenditure decreases and hunger increases. We start regaining weight. So we redouble our efforts by eating even less. This cycle continues until it is intolerable. We are cold, tired, hungry and obsessing about calories. Worst of all, the weight always comes back on.

      At some point, we go back to our old way of eating. Since metabolism has slowed so much, even resuming the old way of eating causes quick weight gain, up to and even a little past the original point. We are doing exactly what our hormones are influencing us to do. But friends, family and medical professionals silently blame the victim, thinking that it is “our fault.” And we ourselves feel that we are a failure.

      Sound familiar?

      All dieters share this same sad story of weight loss and regain. It’s a virtual guarantee. The cycle has been scientifically established, and its truth has been forged in the tears of millions of dieters. Yet nutritional authorities continue to preach that caloric reduction will lead to nirvana of permanent weight loss. In what universe do they live?

       THE CRUEL HOAX

      CALORIC REDUCTION IS a harsh and bitter disappointment. Yet all the “experts” still agree that caloric reduction is the key to lasting weight loss. When you don’t lose weight, they say, “It’s